Method for making multiwall vessels



Jun 1970 E. G. D. RODRIGUES 3,514,839

METHOD FOR MAKING MULTIWALL VESSELS Filed Aug. 2, 1967 3 Sheets-Sheet 1 IN VEN7DR EDOUARD GEORGES DANIEL RODRIGUfiS' 4 Tw /v15 VS June 2, 1970 E. s. D. RODRIGUES 3,514,339

METHOD FOR MAKING MULTIWALL VESSELS 3 Sheets-Sheet 2 Filed Aug. 2. 1967 uvveuron 5000090 GEORGES Mme-1. Rom/sues BY ArmpA/E vs June 2, 1970 E. e. D. RODRIGUES METHOD FOR MAKING MULTIWALL VESSELS 3 Sheets-Sheet 5 Filed Aug. 2. 1967 IN VE N TOR EDOURRD GEORGES DANIEL. RODQIGUES QTTORNEYS United States Patent O METHOD FOR MAKING MULTIWALL VESSELS Edouard Georges Daniel Rodrigues, La Ciotat, France,

assignor to Chantiers Navals de la Ciotat, La Ciotat,

Bouches-du-Rhone, France, a company of France Filed Aug. 2, 1967, Ser. No. 657,761 Claims priority, application 5France, Aug. 26, 1966, 74 37 Int. Cl. lizm 39/02 US. Cl. 29-463 2 Claims ABSTRACT OF THE DISCLOSURE The persent invention has essentially for its object a method for making multiwall vessels or the like, especially pressure vessels designed to contain any product exerting upon its walls a very high pressure, for example a liquefied gas, and presenting a wall thickness e function of said pressure value and of the material said walls are made of.

It is known that if the construction of vessels or the like with wall thicknesses of about 40 to 50 mm. is of a usual practice and presents no technical difilculties, the construction of vessels with wall thicknesses of beyond 50 mm. creates on the contrary embarrassing problems, which are mainly due to the difliculties met in performing a proper welding of the walls. If, from a purely technical point of view, it remains nevertheless possible to weld together walls reaching a thickness of up to 150 mm., it is still obvious that the multiplicity of the difficulties met increase considerably the costs and that, for economical reasons, the constructions requiring such weldings are generally avoided.

But the storage in large quantities of gas, especially when under high pressure, leads to contemplate the construction of vessels with walls reaching a thickness of 200 mm. and more.

The present invention aims at a method for making vessels of the aforementioned type, allowing to obtain very thick walls while still avoiding the hereabove listed drawbacks. The method is remarkable notably in that it consists to imbricate into each other It homothetic and coaxially disposed sheaths of revolution, with a wall thickness value of about e/n, the thickness of each sheath being sufliciently small to allow the performance of a complete penetration Welding, each of said sheaths being itself composed of at least two identical shells assembled through welding, and in providing, between said walls, connecting means, in such a way as to obtain a multilayer vessel wall.

It will be readily appreciated that the method according to the invention allows, by substituting the machining of several relatively thin sheaths to the fabrication of a single sheath with an important thickness, to resolve thus the welding problems which, up to now, practically prohibited the construction of very large containers.

According to another feature of the invention, the vessels are constructed by machining first a set of pairs of homothetic hollow shell portions, two matching shell 3,514,839 Patented June 2, 1970 ice portions having identical dimensions and being juxtaposable along a common junction line which is located substantially in a plane perpendicular to their axis of revolution, each shell portion being provided with an orifice opening upon their border of junction and sufiiciently large to give passage to a man, and by juxtaposing the two smallest shell portions along their junction line, the orifices being in front of each other, so as to constitute a closed container provided with a man-hole, then by welding together, internally and externally, said shell portions along said junction line. then by covering this container with the two next larger shell portions so as to constitute a second container in circumscribing relation with the first, these two shell portions being welded together externally and internally by revolving the internal container, then by rendering the two imbricated containers solid in rotation with each other, their man-holes being coincident, and by repeating this process until the utmost container is achieved.

It will be appreciated that this method allows constituting sheaths which may have any configuration, the only condition to be met by these sheaths being to admit of an axis of revolution. The range of application of the method is hence extremely wide as an innumerable quantity of revolving forms may be imagined.

According to another feature of the invention, a filling substance is introduced within the space comprised between two neighbouring sheaths, in order to allow the transmission of the internal pressure from a sheath to the next and to secure eventually a support for the internal sheath.

A resilient support of this kind allows to admit fairly large construction clearances, and consequently to obtain a relatively reduced cost price.

Moreover, it should be noted that the construction according to the method of the invention is especially simple, as the achieved vessel is constituted by several sheaths, each of which is a standard container.

The possibility of achieving without any welding difficulties multilayer container walls with a very important total thickness, allows to contemplate the construction of very large vessels, submitted to considerable internal pressures.

Finally, it is obvious that a multilayer wall is much safer than an ordinary wall, as, in case of a leakage in one of the containers, the fluid-tightness is secured by the remaining sheaths.

The invention covers also, as new industrial products, the vessels or the like constructed according to the aforementioned process.

The present invention will now be described in greater detail by way of examples with reference to the accompanying drawings, wherein:

FIG. 1 is a perspective view showing a first pair of identical hemispheres each provided with a semi-circular recess, the hemispheres constituting the first or smallest container of one form of vessel;

FIG. 2 is a perspective view showing the hemisphere of FIG. 1 positioned to form a first container;

FIG. 3 is a perspective view identical to FIG. 2 and showing the manner in which the hemispheres are welded together to constitute the first container, the upper hemisphere being partly broken away so that the internal welding may be seen;

FIG. 4 is a perspective view showing a second pair of hemispheres each provided with a semi-circular recess, the hemisphere constituting the second container surrounding the first one;

FIG. 5 is a perspective view showing the hemispheres of FIG. 4 positioned to form a second container surrounding the first container;

FIG. 6 is a perspective view identical to FIG. 5 and showing the manner in which the hemispheres of the second pair are Welded together to constitute the second container, the containers being partly broken away so that the internal welding may be seen;

FIG. 7 is a. perspective view showing the first and second containers rigidly secured with each other; and

FIG. 8 is a perspective view of the completed vessel, with part of the second container broken away.

The basic idea of the invention will now be explained, with reference to the construction of a spherical vessel, composed by two concentric spherical sheaths as shown on FIG. 8. If:

d internal diameter of the internal sphere (C -C e =wall thickness of said internal sphere,

d =internal diameter of the external sphere (C -C e =wall thickness of said external sphere,

e=distance between the two spheres,

p=internal pressure of the internal sphere,

x=pressure within the space comprised between the two spheres,

the stresses and a exerted respectively upon the internal and the external spheres, are given by the fol lowing formulas:

distance e may be considered as constant, we have:

and hence:

As it may be admitted that: w z

it results that:

fi a The internal pressure is consequently determined by the formula:

and hence:

If x is known, the stresses 0' and 0' are easy to calculate.

This calculation supposes that the spheres are at the same temperature. It is possible to adapt the same method of calculation, by taking into account the influence of the temperature.

By calling:

t =temperature of the internal sphere, t temperature of the external sphere,

4 we have:

where:

a =expansion coefiicient at the temperature t of the material the internal sphere is made of,

u =expansion coefficient of the temperature t of the material the external sphere is made of.

If a resilient material is inserted between the two spheres, this material is subjected to a compression which is function of the pressure x. By calling K=compressibility factor of said material, A=actual compression of said material,

we have:

A=Kx and hence:

6d =5d 2Kx The last equation allows to determine x. By supposing that the compression A of the material is related to the pressure by a parabolic function of the type:

where a and [3 are two component compressibility factors, we obtain then the equation:

and hence the value of x.

This may be generalized by writing:

It will be readily seen that it is always possible to determine the number n of the sheaths in such way, that the maximum thickness of these sheaths be smaller than a rated thickness for which the welding is easily performed.

It may also be seen that the thickness of the sheaths is indepedent of the internal pressure, which may be important, and of the diameter of the container, which may also be very important.

Although the calculations hereabove were made with reference to a vessel composed by two spherical sheaths, it will be appreciated that it is readily extended to a vessel composed by n spherical sheaths or by a number n of any sheaths of revolution.

A vessel composed by n spherical sheaths may be achieved as follows:

At the beginning, 11 pairs of hemispheres such as the pair of hemispheres C C on FIG. 1 and C 0 on FIG. 4, are machined out, each of these hemispheres C C' C C exhibiting a preferably semicircular recess 0 0' 0 0' respectively cut out on its free border, the circle corresponding to these recesses having a diameter sufficient to offer a passage to a man. The smallest hemisphere C of one group is inverted over the smallest hemisphere C of the other group, their respective orifices recesses 0 0' being coincident so as to form a circular man-hole O O' (FIG. 2). These two hemispheres C and C, are then welded together along their biggest junction circle. The external weldings S presents no difliculty. The internal welding S' is easy to perform, as a man may penetrate within the container C C' (FIG. 3).

The next in size hemispheres C and C of both groups are then juxtaposed and surround the smallest container C -C1, their respective orifices recesses 0 0' being coincident as previously (FIG. 5). The circular-man-hole O O' of the second container C -C is placed coincident with the man-hole O O' of the first container C -C in order to give passage to the welder. Again, the welding together of these two larger hemispheres C -C at (external welding) and S' (internal welding) presents no difficulty. For the internal welding S' it is suflicient to revolve the internal sphere C -C around an axis XX perpendicular to the junction plane P of the two hemispheres to be welded together. The welder, who is within the innermost sphere C -C' may accede, through the orifice circular man-hole O -O of this smallest sphere, to the junction line between the two outmost hemispheres C -C3 (FIG. 6).

This process is repeated as many times as necessary, the just welded spheres being always rigidly secured to each other, and their man-holes being set to be coincident so as to give access to the junction line of the sphere to be welded next as shown on 'FIG. 7.

Advantageously, each man-hole -O' and 0 -03 may be provided with a circular reinforcement R and R respectively (FIG. 8). By calling:

S2=sectional area of said reinforcement,

,u.=numerical coefiicient,

p=radius of the circular orifice,

e =wall thickness of the sphere,

a=the half-angle of the cone summit, this angle admitting the centre of the sphere as vertex and passing through the circular orifice,

This formula shows that the cross-section of the reinforcement is indepedent from the pressure.

As the values of p, e and on are very close to each other the reinforcements in the different containers are practically identical.

These reinforcements R R may be joined together by bolts B or the like and provided with fluid-tight packings (not shown). In the case where the thickness of the reinforcements is smaller than the distance between two adjacent spheres, some circular rings, fastened by means of bolts, may be provided between said reinforcements.

The distance between two neighbouring spheres being constant, the securing into each other of the spheres, by means of resilient supports, may for instance be achieved, with the help of circular rings A located in parallel planes. These rings may be continuous or not.

The space E comprised between two neighbouring spheres may advantageously be filled with a liquid,-or a resilient material, for instance polystyrol or polyurethane, which is easy to compress.

The use of polystyrol or polyurethane, which are thermal insulators, allows to secure, besides the supporting role, a heat-protection role which is especially interesting in the case of a gas maintained for instance at very low temperature.

The vessels according to the invention may advantageously be utilized for the transportation or the storage of liquefied gas, especially of a gas presenting an important pressure at the air temperature, such as for instance methane.

It is obvious that the practically unlimited choice in the configurations which may be given to the vessels, allows to select, for each case, the most adapted form. Thus for instance, in .order to resist to very high pressures, a spherical configuration will be selected if there are no space problems, while it will be preferable to adopt a cylindric configuration when the space requirements constitute an essential problem.

In the case of vessels 'with a generally cylindric configuration, it is possible to make profit of the advantages offered by a spherical form by providing spherical caps at both ends of these cylinders.

Of course, the invention is by no ways limited to the described methods of embodiment, which are given only by way of example.

What I claim is:

1. A method of making a vessel of revolution designed to contain any product exerting upon its wall a high pressure and having a wall thickness e which is a function of said pressure and a function of the material of which the vessel is made and which exceeds the thickness value for which a complete penetration welding can be performed, said method including the steps of machining a set of n pairs of homothetic shells having an axis of revolution and having a thickness e/n sufiiciently low to allow a complete penetration welding, both shells of a same pair being of identical dimensions and positionable along a common junction line located substantially in a plane perpendicular to said axis of revolution, providing said both shells with a cut-away portion forming a recess upon said junction line and having suflicient dimensions to give passage to a man, positioning the two smallest shells of the aforesaid set along said junction line, the two aforesaid recesses being opposite, so as to form a first container having an axis of revolution and provided with a first man-hole, welding said smallest shells along said junction line both internally and externally in effecting a complete penetration welding, covering said .first container with the two next larger-in-size shells of said set, their axes of revolution being placed coincident with the axis of revolution of said first container, positioning said next larger-in-size shells along their junction line their two recesses being opposite, so as to constitute a second container surrounding said first container and provided with a second man-hole, placing said second man-hole in coincidence with said first manhole to give a passage to a man, welding said next largerin-size shells along their junction line both externally and internally in effecting a complete penetration welding and by revolving said first container relative to said second container, about its axis of revolution, rigidly securing said first and second containers to each other, with said first and second man-holes in coincidence and repeating the aforesaid steps for subsequent containers.

2. A method as claimed in claim 1 further including the step of introducing a filling substance between two neighboring containers whereby transmission of an internal pressure from one container to the next is allowed and whereby a support for the internal container is provided.

References Cited UNITED STATES PATENTS 2,113,060 4/1938 Sandberg 113-120 XR 2,363,990 11/1944 Priebe.

JOHN F. CAMPBELL, Primary Examiner R. B. LAZARUS, Assistant Examiner U.S. Cl. X.R.

mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent: No. 3,5l L,839 Dated June 2, 1970 Inventor(s) Edouard, Georges, Daniel Rodriguefs It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

r- Column 1, line 4, after "assignor" insert: ---of an '1 undividedr'one-half of the entire right, title and interest--- Column 1, line 26, correct the spelling of "present" D Column 1, line 72, after "portions" insert: ---of revolutions--- Column 2, line 11, the period should be a comma.

Column 1, line 43, correct the spelling of "independent SIGNED AND QEAlEl" [im m (SEAL) Atteat:

mm x. JR LAtteafing Offic r Commissioner of Pat nts 

